Basic components and working principles of a Computed Tomography (CT) system are illustrated as follows.
The CT system has a scanner gantry in which a rotation device is equipped. The rotation device is mounted with an X-ray tube, an X-ray collimator and an X-ray detector. In a chamber defined by the scanner gantry, there is provided a patient table. A target object may lie on the patient table, while the rotation device is rotating around the target object. As such, the X-ray tube can irradiate the target object from different angles. The X-ray detector may receive the X-rays which are emitted from the X-ray tube and attenuated when passing through the target object, and obtain corresponding data based on the attenuated X-ray's. CT images may be rebuilt after the data is processed with a computer.
During the X-ray scanning process, the X-ray collimator is normally disposed between the X-ray tube and the target object, which may be beneficial for reducing influence from scattered rays and further improving image quality. The X-ray collimator may control the emitting range and direction of the X-ray beams. By partially sheltering the emitted X-rays, the X-ray collimator can control the X-rays from the tube to irradiate the target object through a specific gap.
Chinese patent application No. 201010543278.5 discloses an X-ray collimator which includes two gates for defining a gap. However, only one of the two gates can be moved to adjust the width of the gap, that is, the width of the gap can only be adjusted in a small range. Therefore, an X-ray collimator which can provide better sheltering effect on the X-rays is required.